Coleen Pugh

Macromonomers, Oligomers and Telechelic Polymers

Although macromonomers and telechelics are oligomers, all three terms can be distinguished from one another by the functionality of their chain ends, and by the nature of the products resulting from the reactions of their chains ends. An oligomer does not necessarily contain any reactive end groups. However, the reactive chain ends are statistically distributed if present, such as in oligomers of condensation polymerizations. A telechelic is an oligomer containing at least one reactive end group, while a macromonomer is generally considered to be an oligomer containing at least one homopolymerizable end group. In contrast, the end groups of a telechelic may undergo chain extension through either condensation polymerization (dicarboxylic, dihydroxylic groups, etc.), addition reactions (e.g. hydrosilation of vinylic groups), or by ring-opening reactions (heterocyclic end groups such as the reaction of glicidyl ethers with carboxylic groups).

Functional Polymers and Sequential Copolymers by Phase Transfer Catalysis. 30. Synthesis of Liquid Crystalline Poly(epichlorohydrin) and Copolymers.

SummaryPoly(epichlorohydrin) (PECH) containing pendant mesogenic units separated from the polymer main chain through spacers of zero to ten methylene units were synthesized and characterized. The synthetic pathway used for the chemical modification of PECH involved the phase transfer catalyzed etherification and esterification of the chloromethyl groups with sodium 4-methoxy-4′-biphenoxide and potassium ω-(4-methoxy-4′-oxybiphenyl)alkanoates. All the resulting polymers, including that with no spacer, present thermotropic liquid crystalline mesomorphism.

Synthesis and group transfer polymerization and copolymerization of p-vinylbenzyl methacrylate

Summaryp-Vinylbenzyl methacrylate was synthesized by the phase transfer catalyzed esterification of potassium methacrylate with p-chloromethylstyrene. p-Vinylbenzyl methacrylate was homopolymerized and copolymerized with methyl methacrylate by group transfer polymerization through the methacryloyl group, resulting in reactive polymethacrylates containing pendant styrene groups.

Induction of smectic layering in nematic liquid crystals using immiscible components III. The effect of lateral n-alkanoyl substituents on the thermotropic behaviour of 2,5-bis[4-(n-perfluoroheptyloctyloxy)benzoyloxy] toluene

Lateral n -alkanoyl substituents were introduced at the benzylic position of 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] toluene by free radical bromination followed by esterification with the corresponding potassium n -alkanoates. All of the transition temperatures of the resulting 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] benzyl n -alkanoates decrease relative to those of 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] toluene and with increasing length of the n -alkanoyl substituent. The SmC-SmA transition decreases the most, thereby stabilizing the SmA mesophase and destabilizing the SmC mesophase. In contrast to the well established concept that lateral substituents disrupt smectic layering, none of the 2,5-bis\[4-(n -perfluoroheptyloctyloxy)benzoyloxy] benzyl n -alkanoates exhibit a nematic mesophase.

Phase transfer Pd(0) catalyzed polymerization reactions

Summary1,4-Bis[2-(4′,4″-diheptyloxyphenyl)ethynyl]benzene and 1,4-bis[2-(3′,3″-dimethyl-4′,4″-diheptyloxyphenyl)ethynyl]benzene were synthesized by a one pot phase transfer Pd(O)/Cu(I) catalyzed three step coupling of 1,4-diiodobenzene with 2-methyl-3-butyn-2-ol and the appropriate aryl halide. Both compounds display mesomorphic behavior similar to that of the analogous 1,2-(4,4′-dialkoxyaryl)acetylenes, except that the temperature window of each phase is stabilized, such that an enantiotropic mesophase is even observed in the derivative containing a methyl branch in the mesogen. Both compounds form mesomorphic EDA complexes with p-chloranil as electron acceptor, and display a depression of the nematic-isotropic transition temperature.

Alkyloxy-substituted CTTV derivatives that exhibit columnar mesophases

The homologous series of 2,3,6,7,10,11,14,15-octaalkyloxytetrabenzo[a,d,g,j]cyclododecatetraenes (CTTV-n) containing n= 4–15 methylenic units in the alkyloxy substituents has been prepared both by alkylation of octhydroxytetrabenzocyclododecatetraenes (CTTV-OH), and by cyclotetramerization of the corresponding 3,4-(dialkyloxy)benzyl alcohols using excess CF3CO2H. CTTV-4 is crystalline. All other compounds display an enantiotropic columnar mesophase in addition to melting and crystallization transitions. The phase-transition temperatures of the CTTV-n compounds prepared by cyclotetramerization are lower than those synthesized by etherification of CTTV-OH. Melting and isotropization temperatures decrease in a continuous manner as n increases, without any odd–even alternation.

Columnar mesophases of cyclic trimers of disubstituted acetylenes

Hexa(4-alkyphenoxymethyl)benzenes, 4(with n= 4, 7, 9) were prepared by the alkylation of hexa(bromomethyl)-benzene and/or Cp2Co catalysed cyclotrimerization of the corresponding 1,4-di(4-alkylphenoxy)but-2-yne monomer, 2. The derivative 4(n= 4) is crystalline. The derivative 4(n= 7) displays an enantiotropic columnar mesophase and compound 4(n= 9) displays a monotropic columnar mesophase whose polarized optical microscopic textures are typical of Dho mesophases. An additional columnar mesophase of the derivative 4(n= 7) is monotropic. Hexa(4-alkoxyphenyl)benzenes, 3(n= 4–9) were prepared by PdCl2(PhCN)2 catalysed cyclotrimerizations of the corresponding 1,2-di(4-alkoxyphenyl)acetylenes, 1. The derivatives 3(n= 6–9) form anisotropic glasses whose columnar mesophases become more fluid as the temperature approaches isotropization. Methyl branches in either the mesogen or the alkoxy substituents promotes solidification, whether it is to a crystalline phase or to an anisotropic glass.